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WM W_ 1301 MARINA VILLAGE PARKWAY <br /> SUITE 200 <br /> ALAMEDA,CALIFORNIA 94501 <br /> TEL: (510)769-0100 <br /> ENGINEERING-SCIENCE, INC. FAX: (510)769-9244 <br /> 4 February 1992 <br /> Ref: SY132.31 <br /> San Joaquin County O <br /> Public Health Services <br /> Environmental Health Division FEB 10 1992 <br /> P. O. Box 2009 <br /> 445 North San Joaquin Street ENVIRONMENTAL HEALTH <br /> Stockton, California 95201 PERMIT/SERVICES <br /> Attention: Mr. Michael J. Infurna, REHS <br /> Subject: Greyhound Termina18969, 121 South Center Street, Stockton, California <br /> Dear Mr. Infurna: <br /> The purpose of this letter is to respond to your questions concerning analytical <br /> laboratory results presented in Engineering-Science, Inc.'s (ES's) document entitled <br /> "Preliminary Site Investigation Report, Greyhound Terminal Location 8969, Stockton, <br /> California" dated November 27, 1991. Your questions were transmitted to ES during our <br /> telephone conversation of January 27, 1992. <br /> Galson Laboratories of Syracuse, New York performed the chemical analysis of soil <br /> and groundwater samples collected for this investigation. Galson Laboratories is a <br /> California Environmental Protection Agency, Department of Toxic Substance Control <br /> (DTSC) certified hazardous waste laboratory (Certification Number 348). <br /> The following questions and responses are listed in the order of discussion during our <br /> telephone conversation of January 27, 1992: <br /> 1) Dilution factors for soil samples - dilution factors for laboratory analyses of soil <br /> samples ranged from 1 to 1,000 for total petroleum hydrocarbons (TPH) and <br /> aromatic hydrocarbons (BTEX). The samples are diluted because of matrix <br /> interferences and contaminant masking. One contaminant is frequently in such <br /> greater abundance in relation to other contaminants that to quantify the high <br /> concentration contaminant the sample must be diluted. Because of the dilution, <br /> quantification of lower concentration contaminants may not be possible. <br /> You requested that in order to quantify all contaminants of concern, both low <br /> and high dilution factor aliquots of the same sample should be analyzed. <br /> However, pre-knowledge of low/high contaminant concentrations would be <br /> required. No field measurement technique that would supply this information is <br /> known. In addition, a low/high analysis is not routinely run on samples unless <br /> specifically requested by the laboratory client (personal communication between <br /> Mr. Neal Siler of ES-Alameda and Mr. Richard Wood of ES Laboratories, <br /> January 30, 1992; personal communication between Neal Siler of ES-Alameda <br /> and Ms. Eva Galson of Galson Laboratories, January 30, 1992). <br /> A PARSONS COMPANY <br />